In U.S. Pat. No. 3,878,011, there is disclosed and claimed a method of producing a pile fabric comprising the steps of feeding a pre-formed base fabric with a layer of adhesive to a tuft-attaching station extending transversely of the direction of feed of the base fabric. The adhesive has a composition such that its viscosity decreases on heating and is in a sufficiently sticky condition at the attaching station to cause yarn pressed into the adhesive to adhere thereto. A row of tuft-forming lengths of pile yarn is brought to said station from a source presenting yarn ends in a row. A first part of each tuft-forming length is pressed into the layer of adhesive to attach said part to the base fabric, with a further part of each tuft-forming length projecting from the adhesive layer. The base fabric is fed with said row of tuft-forming lengths adhering thereto, away from the attaching station. Then the viscosity of said adhesive is temporarily reduced to secure the tuft-forming lengths to the base fabric by temporarily raising its temperature.
Also disclosed in said prior patent is an apparatus for the production of pile fabric comprising the combination of means for feeding a pre-formed base fabric and an adhesive along a feed path through a pile attaching station. First heater means supplied heat to the adhesive approaching said attaching station. Feeding means feeds a row of tuft-forming lengths of pile yarn from a source thereof to the attaching station and pressing means presses a part of each tuft-forming length into the adhesive at the attaching station. Second heater means supplies heat to the adhesive after passage through the attaching station. The second heat means is operative, during use of the apparatus, to raise the temperature of the adhesive temporarily.
The present invention is concerned with certain improvements in, or modifications of, the method claimed isn said prior patent and is further concerned with the provision of a new or improved form of apparatus for the performance of such improved or modified method.
Referring firstly to the method of making the pile fabric, a first aspect of the present invention relates to an additional operation which may be performed on the fabric to overcome or reduce unevenness of pile height and variability as to the strength of attachment of the pile tufts through the adhesive to the base fabric.
In practicing the method disclosed and claimed in said prior patent, the reduction of the viscosity of the adhesive by raising its temperature after part of each tuft-forming length of yarn has been pressed into the adhesive, that is to say implanted therein, may cause bubbles to be formed in the layer of adhesive. This causes certain of the implanted tufts to rise to varying degrees relative to the base fabric, with the result that the surface of the pile fabric becomes noticeably uneven. The formation of bubbles which disturb the adhesive layer can result from the presence of air or of volatile materials, for example water or oil, on or in the base fabric or in the adhesive layer. The base fabric is typically formed of hessian and this material tends to retain moisture until it is heated. The heating of the adhesive is usually affected by means of a hot metal plate which contacts the face of the base fabric remote from the adhesive layer. This plate makes it difficult for air and vapors to escape from the base fabric other than through the adhesive layer.